Twenty Thousand Leagues Under the Sea is a novel by French writer Jules Verne. It is a classic of early science fiction

The story follows the adventures of Professor Pierre Aronnax, a French marine biologist, who is finds himself onboard a mysterious submarine, the Nautilus. The Nautilus was built in secret and now roams the seven seas free from any government interference. The technology of the Nautilus is far beyond the naval technology of the time and its creator is the secretive Captain Nemo who has exiled himself from civilization in his creation.

The title of the novel refers to the distance traveled while under the sea and not to a depth. 20,000 leagues is nearly three times the circumference of the Earth.